1. Field of Invention
The present invention relates to an optimised rear dxc3xa9railleur device for a bicycle, in particular, however, not exclusively appropriate for bicycles also comprising a front dxc3xa9railleur and a gearshift system, the unit being controlled by a synchronized control handle.
2. Description of Related Art
An arrangement of two dxc3xa9railleurs, front and rear, controlled by a single handle is known from the European Patent Application No. 95450012.0.
This arrangement is particularly interesting for the user with regards to riding, however, the particular advantage set forth in the present application, does not represent a direct interest to the user, rather it is the limitation of the chain length.
The fact namely that the number of combinations of the disks and pinions is reduced into a subunit determined by the entirety of combinations corresponding to the product of the number of pinions by the number of disks, is due to the fact that the alignment of the chain is optimised and the length of the chain reduced.
Moreover, the market requires an improved ground clearance, in particular in the case of off-road bicycles, and it becomes clear that the rear dxc3xa9railleur is particularly exposed to shocks and to getting caught, in particular when a great chain length has to be taken up.
The dxc3xa9railleur according to the present invention moreover proposes a dxc3xa9railleur, the ground clearance of which is considerably increased and the operation of which does not disturb the conception of the bicycle frame so that it can be mounted on the existing bicycle fleet without modification, on condition that a means for limiting the chain crossing is preferably present, so as to reduce the length of the chain, the fabrication of which necessitates pieces which can directly be industrially manufactured, the operation of which is the same for the user, the putting into service of which allows the conservation of the pinion and disk sets existing on the bicycle, and the cost of which remains within the range of prices of the dxc3xa9railleurs on the market.
For that purpose, the inventive dxc3xa9railleur device is characterized in that it is equipped with a front dxc3xa9railleur, a chain connecting a set of pinions and at least one disk and, if the case may be, a synchronized control limiting the combinations for an adapted chain alignment and for reducing the chain length necessary in the case of several disks, characterized in that it comprises:
a rotatable base provided with a return spring forcing the so base in anti-clockwise direction
guiding/dxc3xa9railleur means fixedly connected to the base, and
a movable tension plate fixedly connected to the guiding/dxc3xa9railleur means.
According to a particular embodiment, the movable tension plate comprises a supporting arm, a tension arm mounted pivotable relative to the supporting arm, and a first and a second tension roller mounted freely rotatable on the ends of the tension arm, as well as a spring forcing the tension arm in anti-clockwise direction, whereby the chain passes over the first tension roller and under the second tension roller.
In particular, the tension arm is mounted onto an axis pivoting relative to the supporting arm, and the axis is essentially arranged in the centre of the tension arm or, according to a variant the axis coincides with the rotation axis of the second roller.
According to a further characteristic, the guiding/dxc3xa9railleur means comprises a deformable parallelogram carrying at its end, immediately downstream of the movable tension plate and in the alignment thereof, a guiding/dxc3xa9railleur roller mounted freely rotatable, whereby the chain passes over this guiding/dxc3xa9railleur roller.
An improvement provides that the guiding/dxc3xa9railleur roller is supported by means for adjusting the translation in the plane of the chain.
Moreover, the guiding/dxc3xa9railleur roller comprises additional means for lateral guidance such as at least one flange.
In a variant which is particularly advantageous for the fabrication as well as for the user""s convenience due to an improvement of the dxc3xa9railleur quality, connection means interposed between the movable tension plate and the guiding/dxc3xa9railleur means are provided so as to restrain the tensional stress of the chain and the return stress of the guiding means.